The hypotensive effect of 25 mg, 50 mg, 75 mg, 100 mg and 0 mg of atenolol daily were compared in a double-blind within-patient study. The fall in blood pressure with 25 mg daily was not significantly different than with 100 mg. The dose response curve lies between 0 and 25 mg daily. Cardiac beta-blockade (measured by suppression of exercise tachycardia) was not maximal with 25 mg of atenolol daily. The dose response curves for beta-blockade and the hypotensive effect are not parallel.